The duration of Foal Eagle has been shortened to a month, with no major US strategic assets such as supercarriers and nuclear subs expected to show up.

Some observers said Seoul and Washington are apparently playing low-key amid a let-up in North Korea's provocations. The communist nation's leader Kim Jong-un plans to have back-to-back summit talks with the South's President Moon Jae-in and US President Donald Trump this spring.

The allies' defense authorities stressed that there's no big change in the number of participating troops, program and the "intensity" of the exercise.

In particular, they pointed out, the two sides' Marines are conducting a massive Ssangyong (double dragon) amphibious landing drill in Korea through April 8.

It involves the USS Wasp, the US Navy's 40,500-ton multipurpose amphibious assault ship carrying F-35B stealth fighter aircraft and the USS Bonhomme Richard, another vessel of the same class. The ships are called "quasi aircraft carriers."

The allies will also kick off a two-week Key Resolve command-post war game April 23, in which as many as 12,200 US troops will be mobilized.

Pyongyang has long denounced the joint drills as a symbol of Washington's hostile policy and rehearsal for invasion.

The 28,500-strong US Forces Korea is already stationed in Korea as a legacy of the 1950-53 Korean War that ended in an armistice.

The issue of replacing the Armistice Agreement with a peace treaty is likely to be discussed in the upcoming summits. (Yonhap)